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In this article we will be looking at the Methods of Manufacture of Rubber Castors.

Polymer based Castors are manufactured from a range of different material types including both Natural materials and Synthetic materials. The most commonly used materials for Castor manufacture would be Natural Rubber (NR), Styrene-Butadine (SBR), Nitrile Rubber and Polyurethane.

Each material offering differing features and properties. In this article we will focus on the Black Rubber Castor which is typically manufactured from an NR/SBR blend, much like an automotive car tire.

The Start of a Castors Life........

The First stage of Castor manufacturing is to select the raw material for the wheel.

RAW NATURAL RUBBER (BROWN) AND RAW SBR (WHITE)

Raw Rubber offers benefits such as flexibility, however in order to gain the required properties of the rubber a compounding process (mixing) is required. The Raw Rubber is mixed with various fillers and additives, which include:

The Rubber is mixed and calendared into sheets of “Rubber Compound” which is then used for producing the castors wheels.

CALENDARING OF RUBBER CALENDARED RUBBER

Moulding of Rubber Castors Wheel...........

The Calendared Rubber is then cut into “Blanks” (pieces of accurately weighed rubber) and placed into the mould tool. The mould tool will produced to the required size and shape of the Castor Wheel. The Wheel Hub is then put into the mould (with a pre-treatment of bonding adhesive) along with the rubber Blanks. The Mould is closed and held under pressure and temperature. The time period can be as short as 10 minutes for a 50mm Castor to 30mins for a 200mm Castor. The curing temperature for NR/SBR would be approx. 150 Deg C.

CASTOR WHEEL RUBBER MOULD

After moulding is complete the mould is opened and the Rubber Castor Wheel Removed. After a period of cooling the wheel is assembled into the Castor Fork (Bracket).